What is a chemical bond? — A force of attraction that holds two or more atoms together. Bonds form when atoms achieve a more stable (lower energy) arrangement, usually by completing their outer electron shell.

What is an ionic bond? — A bond formed by the transfer of electrons from a metal to a nonmetal, creating oppositely charged ions (cation + anion) that attract each other. Example: Na⁺Cl⁻ (table salt).

What is a covalent bond? — A bond formed by the sharing of electrons between two nonmetal atoms. Both atoms achieve a full outer shell by sharing. Example: H₂, H₂O, CO₂.

What is the difference between polar and nonpolar covalent bonds? — Polar: Electrons shared unequally because atoms have different electronegativities (e.g., H₂O, HCl). Nonpolar: Electrons shared equally between identical or similar atoms (e.g., H₂, O₂, CH₄).

What is a metallic bond? — Bonding in metals where positively charged metal ions are surrounded by a "sea" of delocalized electrons. Explains metals' conductivity, malleability, and ductility.

What are Lewis dot structures? — Diagrams showing valence electrons of atoms as dots around the element symbol. Used to visualize bonding and lone pairs in molecules. Each dot represents one valence electron.

What is the octet rule? — Atoms tend to form bonds until they are surrounded by 8 electrons in their outer shell (like noble gases). Hydrogen is an exception — it only needs 2 electrons.

What is a single bond, double bond, and triple bond? — Single bond: 1 shared pair (2 electrons) — e.g., H–H. Double bond: 2 shared pairs (4 electrons) — e.g., O=O. Triple bond: 3 shared pairs (6 electrons) — e.g., N≡N. Stronger and shorter as bond order increases.

What is electronegativity and how does it determine bond type? — The tendency of an atom to attract shared electrons. Difference < 0.4 = nonpolar covalent. Difference 0.4–1.7 = polar covalent. Difference > 1.7 = ionic bond.

What is VSEPR theory? — Valence Shell Electron Pair Repulsion theory — electron pairs around a central atom repel each other and arrange themselves to be as far apart as possible, determining molecular shape.

What is the molecular geometry of water (H₂O)? — Bent (V-shaped). Central oxygen has 2 bonding pairs and 2 lone pairs. Bond angle ≈ 104.5°. Polar molecule due to asymmetric shape and O–H bond polarity.

What is the molecular geometry of ammonia (NH₃)? — Trigonal pyramidal. Central nitrogen has 3 bonding pairs and 1 lone pair. Bond angle ≈ 107°. Polar molecule.

What is the molecular geometry of methane (CH₄)? — Tetrahedral. Carbon has 4 bonding pairs, no lone pairs. Bond angle = 109.5°. Nonpolar molecule — symmetrical shape cancels out bond dipoles.

What is the molecular geometry of carbon dioxide (CO₂)? — Linear. Carbon has 2 double bonds, no lone pairs. Bond angle = 180°. Nonpolar overall — polar C=O bonds cancel out due to symmetry.

What is hybridization in chemistry? — The mixing of atomic orbitals to form new hybrid orbitals with different shapes and energies. sp³ (tetrahedral), sp² (trigonal planar), sp (linear).

What is a hydrogen bond? — A strong intermolecular attraction between a hydrogen atom bonded to F, O, or N and the lone pair of another F, O, or N atom. Explains water's high boiling point and surface tension.

What are London dispersion forces (LDF)? — The weakest intermolecular force — temporary dipoles caused by random electron movement attracting neighboring atoms/molecules. Present in ALL molecules. Stronger in larger, heavier molecules.

What are dipole-dipole interactions? — Intermolecular attractions between the positive end of one polar molecule and the negative end of another. Stronger than London forces but weaker than hydrogen bonds.

What determines the strength of intermolecular forces? — Stronger IMFs = higher boiling point, melting point, and viscosity. Order of strength: London forces < dipole-dipole < hydrogen bonds < ionic interactions.

What is a coordinate (dative) covalent bond? — A covalent bond where both electrons in the shared pair come from the same atom. Example: NH₄⁺ (ammonium ion) — nitrogen donates both electrons to H⁺.

What is bond length and how does it relate to bond order? — The distance between the nuclei of two bonded atoms. As bond order increases (single→double→triple), bond length decreases and bond strength increases.

What is resonance in chemistry? — When a molecule cannot be represented by a single Lewis structure — the actual structure is an average (resonance hybrid) of multiple structures. Example: benzene (C₆H₆), ozone (O₃).

What is a sigma (σ) bond vs a pi (π) bond? — Sigma bond: Head-on orbital overlap — forms first in any bond (all single bonds are sigma). Pi bond: Side-on orbital overlap — forms in addition to sigma in double and triple bonds.

What makes water such an unusual molecule? — Bent shape + high electronegativity of O + 2 lone pairs create strong hydrogen bonds. This gives water an abnormally high boiling point, specific heat capacity, and surface tension.

What is the difference between intramolecular and intermolecular forces? — Intramolecular: Forces within a molecule (chemical bonds — ionic, covalent, metallic). Intermolecular: Forces between separate molecules (LDF, dipole-dipole, hydrogen bonds). IMFs are much weaker.